Background synchronization of data objects is a process for applying bulk changes to objects in a data store. In some situations, sets of changes may need to be applied in bulk to the items in a data store, such as a Messaging Application Programming Interface (MAPI) compliant application's data objects. For example, sets of items may need to be mirrored from a customer relationship management (CRM) system to an e-mail application store or a data set may need to be imported into a MAPI store. In conventional systems, main application threads are blocked while the bulk data operation is performed. This may result in users experiencing delays and non-responsive applications.